Variable magnification optical system and imaging apparatus

ABSTRACT

A variable magnification optical system substantially consists of a first lens-group having positive refractive-power, and which is fixed during magnification change, a second lens-group having negative refractive-power, a third lens-group having negative refractive-power, a fourth lens-group having negative refractive-power, an aperture stop, which is fixed during magnification change, and a fifth lens-group having positive refractive-power, and which is fixed during magnification change, in this order from an object-side along an optical-axis. The second, third and fourth lens-groups move in such a manner that a distance between the first lens-group and the second lens-group constantly becomes longer and a distance between the second lens-group and the third lens-group constantly becomes longer, compared with a wide-angle end, and a distance between the third lens-group and the fourth lens-group and a distance between the fourth lens-group and the fifth lens-group change when magnification is changed from the wide-angle end to a telephoto end.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of PCT/JP2012/005428 filed on Aug.29, 2012, which claims foreign priority to Japanese Application No.2011-187419 filed on Aug. 30, 2011. The entire contents of each of theabove applications are hereby incorporated by reference

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a variable magnification optical systemand an imaging apparatus. In particular, the present invention relatesto a variable magnification optical system usable in a video camera, anelectronic still camera and the like, and appropriate especially for asurveillance camera, and also to an imaging apparatus including thevariable magnification optical system.

2. Description of the Related Art

Conventionally, variable magnification optical systems for CCTV(Closed-circuit Television) were developed, as optical systems forimaging apparatuses, such as a video camera, an electronic still camera,and a surveillance camera, which use imaging devices, such as a CCD(Charge Coupled Device) and a CMOS (Complementary Metal OxideSemiconductor), as recording media. As such variable magnificationoptical systems for CCTV, many optical systems with four group structurehave been proposed, because they have many advantages, such as thesimplicity of the lens barrel and variable magnification mechanisms andthe easiness of handling (please refer, for example, to JapaneseUnexamined Patent Publication No. 9(1997)-258102 (Patent Document 1),U.S. Pat. No. 6,512,637 (Patent Document 2), U.S. Patent ApplicationPublication No. 20010019455 (Patent Document 3), Japanese UnexaminedPatent Publication No. 2003-287678 (Patent Document 4), U.S. PatentApplication Publication No. 20040042075 (Patent Document 5), JapaneseUnexamined Patent Publication No. 2004-126631 (Patent Document 6), andJapanese Unexamined Patent Publication No. 2005-084409 (Patent Document7)).

Further, although the structure of five-group optical systems is morecomplicated than the structure of four-group optical systems, manyoptical systems with five group structure have been also proposed togive excellent optical performance (please refer, for example, to U.S.Pat. No. 5,636,060 (Patent Document 8) and Japanese Unexamined PatentPublication No. 2011-081063 (Patent Document 9)).

SUMMARY OF THE INVENTION

In four-group variable magnification optical systems, as disclosed inPatent Documents 1 through 7, an optical system consists of a first lensgroup having positive refractive power, and which is fixed duringmagnification change, a second lens group having negative power, andwhich moves during magnification change, a third lens group havingnegative refractive power, and which moves during magnification change,and a fourth lens group having positive refractive power, and which isfixed during magnification change, which are in this order from anobject side. If the magnification ratio of such an optical system istried to be increased while its high optical performance is maintained,the outer diameter of the first lens group becomes large. Therefore,there is a drawback that the weight becomes heavy. On the contrary, ifthe size of such an optical system is tried to be reduced, the negativerefractive power of the second lens group becomes too strong. Therefore,there is a drawback that the optical performance of the optical systembecomes lower.

As a method for solving such problems, Patent Document 8 proposes afive-group variable magnification optical system consisting of a firstlens group having positive refractive power, and which is fixed duringmagnification change, a second lens group having negative refractivepower, and which moves during magnification change, a third lens grouphaving negative refractive power, and which moves during magnificationchange, a fourth lens group having negative refractive power, and whichmoves during magnification change, and a fifth lens group havingpositive refractive power, and which is fixed during magnificationchange, which are in this order from the object side. In this variablemagnification optical system, the second lens group in theaforementioned four-group variable magnification optical system isdivided into lens groups. The divided lens groups become close to eachother at a wide-angle end and at a telephoto end, and become away fromeach other in a middle variable magnification range. Many features arenot clear because detailed lens data are not disclosed. However, sincethis lens structure does not have any difference from the structure ofthe conventional four-group variable magnification optical system at awide-angle end and at a telephoto end. Therefore, it is impossible tosolve the aforementioned problems.

Patent Document 9 discloses a variable magnification optical system witha high variable magnification ratio. However, the diameter of the firstlens group is large, and the weight is heavy.

In view of the foregoing circumstances, it is an object of the presentinvention to provide a variable magnification optical system withexcellent optical performance while the size of the optical system issmall and the weight of the optical system is light, and an imagingapparatus including the variable magnification optical system.

A variable magnification optical system of the present inventionsubstantially consists of:

a first lens group having positive refractive power, and which is fixedduring magnification change;

a second lens group having negative refractive power;

a third lens group having negative refractive power;

a fourth lens group having negative refractive power; and

a fifth lens group having positive refractive power, and which is fixedduring magnification change, which are in this order from an objectside. The second lens group, the third lens group and the fourth lensgroup move in such a manner that a distance between the first lens groupand the second lens group constantly becomes longer and a distancebetween the second lens group and the third lens group constantlybecomes longer, compared with a wide-angle end, and a distance betweenthe third lens group and the fourth lens group changes and a distancebetween the fourth lens group and the fifth lens group changes whenmagnification is changed from the wide-angle end to a telephoto end.

It is desirable that the fourth lens group in the variable magnificationoptical system of the present invention temporarily moves toward theobject side and reversely moves toward an image side when magnificationis changed from the wide-angle end to the telephoto end.

Further, it is desirable that the distance between the third lens groupand the fourth lens group in the variable magnification optical systemof the present invention is the shortest when a focal length is closerto the wide-angle end than to the telephoto end during magnificationchange, and that the distance at the wide-angle end is longer than thedistance at the telephoto end.

It is desirable that the first lens group in the variable magnificationoptical system of the present invention substantially consists of a1f-th lens group having negative refractive power, and whichsubstantially consists of two negative lenses, a 1m-th lens group havingpositive refractive power and a 1r-th lens group having positiverefractive power, which are in this order from the object side, and thatfocusing is performed by moving the 1m-th lens group in the direction ofan optical axis.

In this case, it is desirable that the 1m-th lens group is a cementedlens substantially consisting of a concave meniscus lens with its convexsurface facing the object side and a biconvex lens, which are in thisorder from the object side.

In the variable magnification optical system of the present invention,it is desirable that the following conditional formula (1) is satisfiedwhen the focal length of the second lens group is f2 and the focallength of the third lens group is f3:0.10<f2/f3<2.00  (1).

Further, it is desirable that the second lens group in the variablemagnification optical system of the present invention substantiallyconsists of only a concave meniscus lens with its convex surface facingthe object side.

In this case, it is desirable that the following conditional formula (2)is satisfied when the refractive index of the concave meniscus lens isLN2:2.0≦LN2  (2).

Here, the sign of the refractive power and the surface shape of each ofthe aforementioned lenses are considered in a paraxial region when thelens is an aspherical lens.

In the above descriptions, the number of lenses is the number of lenses,as composition elements. For example, when plural single lenses made ofdifferent materials from each other are cemented together to form acemented lens, the number of the single lenses constituting the cementedlens is counted.

Further, the term “convex meniscus lens” refers to a meniscus lenshaving positive refractive power. The term “concave meniscus lens”refers to a meniscus lens having negative refractive power.

The imaging apparatus of the present invention includes the variablemagnification optical system of the present invention, as describedabove.

The variable magnification optical system of the present inventionsubstantially consists of a first lens group having positive refractivepower, and which is fixed during magnification change, a second lensgroup having negative refractive power, a third lens group havingnegative refractive power, a fourth lens group having negativerefractive power, and a fifth lens group having positive refractivepower, and which is fixed during magnification change, which are in thisorder from an object side. Further, the second lens group, the thirdlens group and the fourth lens group move in such a manner that adistance between the first lens group and the second lens groupconstantly becomes longer and a distance between the second lens groupand the third lens group constantly becomes longer, compared with awide-angle end, and a distance between the third lens group and thefourth lens group changes and a distance between the fourth lens groupand the fifth lens group changes when magnification is changed from thewide-angle end to a telephoto end. Therefore, it is possible to achieveexcellent optical performance while the size of the optical system issmall and the weight of the optical system is light.

The imaging apparatus of the present invention includes the variablemagnification optical system of the present invention. Therefore, it ispossible to obtain images with high image qualities while the size ofthe imaging apparatus is small and the weight of the imaging apparatusis light.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1, Sections A through C are cross sections illustrating the lensstructure of a variable magnification optical system according to anembodiment of the present invention (also Example 1);

FIG. 2, Sections A through C are cross sections illustrating the lensstructure of a variable magnification optical system in Example 2 of thepresent invention;

FIG. 3, Sections A through C are cross sections illustrating the lensstructure of a variable magnification optical system in Example 3 of thepresent invention;

FIG. 4, Sections A through C are cross sections illustrating the lensstructure of a variable magnification optical system in Example 4 of thepresent invention;

FIG. 5, Sections A through C are cross sections illustrating the lensstructure of a variable magnification optical system in Example 5 of thepresent invention;

FIG. 6, Sections A through C are cross sections illustrating the lensstructure of a variable magnification optical system in Example 6 of thepresent invention;

FIG. 7, Sections A through L are aberration diagrams of the variablemagnification optical system in Example 1 of the present invention;

FIG. 8, Sections A through L are aberration diagrams of the variablemagnification optical system in Example 2 of the present invention;

FIG. 9, Sections A through L are aberration diagrams of the variablemagnification optical system in Example 3 of the present invention;

FIG. 10, Sections A through L are aberration diagrams of the variablemagnification optical system in Example 4 of the present invention;

FIG. 11, Sections A through L are aberration diagrams of the variablemagnification optical system in Example 5 of the present invention;

FIG. 12, Sections A through L are aberration diagrams of the variablemagnification optical system in Example 6 of the present invention; and

FIG. 13 is a schematic diagram illustrating the configuration of animaging apparatus according to an embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described in detail withreference to drawings. FIG. 1, Sections A through C illustrate crosssections of a structure example of a variable magnification opticalsystem according to an embodiment of the present invention. Thestructure example illustrated in FIG. 1, Sections A through C is commonto the embodiment and a variable magnification optical system in Example1, which will be described later. In FIG. 1, Sections A through C, theleft side is the object side, and the right side is the image side.

This variable magnification optical system consists of first lens groupG1 having positive refractive power, and which is fixed duringmagnification change, second lens group G2 having negative refractivepower, third lens group G3 having negative refractive power, fourth lensgroup G4 having negative refractive power, aperture stop St, which isfixed during magnification change, and fifth lens group G5 havingpositive refractive power, and which is fixed during magnificationchange, which are in this order from an object side along optical axisZ. Further, second lens group G2, third lens group G3 and fourth lensgroup G4 move in such a manner that a distance between first lens groupG1 and second lens group G2 constantly becomes longer and a distancebetween second lens group G2 and third lens group G3 constantly becomeslonger, compared with a wide-angle end, and a distance between thirdlens group G3 and fourth lens group G4 changes and a distance betweenfourth lens group G4 and fifth lens group G5 changes when magnificationis changed from the wide-angle end to a telephoto end. Here, aperturestop St illustrated in FIG. 1 does not necessarily represent the sizenor the shape of aperture stop St, but the position of aperture stop Ston optical axis Z.

When this variable magnification optical system is applied to an imagingapparatus, it is desirable to arrange a cover glass, a prism, andvarious filters, such as an infrared ray cut filter and a low-passfilter, between the optical system and image plane Sim based on thestructure of the camera side on which the lens is mounted. Therefore,FIG. 1 illustrates an example in which parallel-flat-plate-shapedoptical members PP1 and PP2, which are assumed to be such elements, arearranged between fifth lens group G5 and image plane Sim.

In conventional four-group variable magnification optical systems, asdisclosed in Patent Documents 1 through 7, an optical system consists ofa first lens group having positive refractive power, and which is fixedduring magnification change, a second lens group having negative power,and which moves during magnification change, a third lens group havingnegative refractive power, and which moves during magnification change,and a fourth lens group having positive refractive power, and which isfixed during magnification change, which are in this order from anobject side. If the magnification ratio of such an optical system istried to be increased while its high optical performance is maintained,the outer diameter of the first lens group becomes large. Therefore,there is a drawback that the weight becomes heavy. On the contrary, ifthe size of such an optical system is tried to be reduced, the negativerefractive power of the second lens group becomes too strong. Therefore,there is a drawback that the optical performance of the optical systembecomes lower.

As a method for solving such problems, Patent Document 8 proposes afive-group variable magnification optical system consisting of a firstlens group having positive refractive power, and which is fixed duringmagnification change, a second lens group having negative refractivepower, and which moves during magnification change, a third lens grouphaving negative refractive power, and which moves during magnificationchange, a fourth lens group having negative refractive power, and whichmoves during magnification change, and a fifth lens group havingpositive refractive power, and which is fixed during magnificationchange, which are in this order from the object side. In this variablemagnification optical system, the second lens group in theaforementioned four-group variable magnification optical system isdivided into lens groups, and the divided lens groups become close toeach other at a wide-angle end and at a telephoto end, and become awayfrom each other in a middle variable magnification range. Many featuresare not clear because detailed lens data are not disclosed. However,since this lens structure does not have any difference from thestructure of the conventional four-group variable magnification opticalsystem at a wide-angle end and at a telephoto end. Therefore, it isimpossible to solve the aforementioned problems. It is conceivable thatthe main purpose of Patent Document 8 is to improve its performance inthe middle variable magnification range.

In Patent Document 9, a second lens group in the aforementionedfour-group variable magnification optical system is divided into lensgroups, and a distance between the divided lens groups becomes theshortest when a variable magnification position is closer to thetelephoto end than to the wide-angle end during magnification change. Itis conceivable that the main purpose of this structure is to obtain ahigh variable magnification ratio. The diameter of a first lens groupremains large, and the weight remains heavy.

In the variable magnification optical system according to an embodimentof the present invention, the feature of dividing the second lens groupin the four-group variable magnification optical system into lens groupsis similar. However, when magnification is changed from a wide-angle endto a telephoto end, a distance between the divided lens groups (secondlens group G2 and third lens group G3 in the five-group variablemagnification optical system) constantly increases, compared with thewide-angle end, and this feature is different. This structure cansuppress a spherical aberration, which tends to be excessively correctedespecially on the telephoto side when a magnification ratio is increasedwhile the small size is maintained.

When magnification is changed, if second lens group G2 and third lensgroup G3 are moved while first lens group G1 and fifth lens group G5 arefixed with respect to an image plane, a focal position fluctuates. Tocorrect such movement of the focal point, fourth lens group G4 in thevariable magnification optical system according to an embodiment of thepresent invention temporarily moves toward the object side and reverselymoves toward the image side when magnification is changed from awide-angle end to a telephoto end.

Further, a distance between third lens group G3 and fourth lens group G4in the variable magnification optical system according to an embodimentof the present invention is the shortest when a focal length is closerto the wide-angle end than to the telephoto end during magnificationchange, and the distance at the wide-angle end is longer than thedistance at the telephoto end. Therefore, it is possible to suppress afluctuation of curvature of field in a middle variable magnificationrange.

Further, the variable magnification optical system according to anembodiment of the present invention satisfies the following conditionalformula (1) when the focal length of a second lens group is f2, and thefocal length of a third lens group is f3. If the value is lower than thelower limit of conditional formula (1), the refractive power of secondlens group G2 becomes too strong, and astigmatism mainly at a wide-angleend and distortion become worse. On the contrary, if the value exceedsthe upper limit of conditional formula (1), the refractive power ofthird lens group G3 becomes too strong, and a spherical aberration at atelephoto end becomes worse.0.10<f2/f3<2.00  (1)

Further, second lens group G2 of the variable magnification opticalsystem according to an embodiment of the present invention consists ofonly concave meniscus lens L8 with its convex surface facing the objectside. Therefore, it is possible to suppress the diameter of first lensgroup G1 to be small while the total length of the lens is minimized byminimizing the lens length of second lens group G2.

Here, when the refractive index of concave meniscus lens L8 is LN2, thefollowing conditional formula (2) is satisfied. When conditional formula(2) is satisfied, it is possible to reduce the curvature of concavemeniscus lens L8, and to suppress an increase of a spherical aberrationat a telephoto end.2.0≦LN2  (2)

Further, the first lens group in the variable magnification opticalsystem according to an embodiment of the present invention consists of1f-th lens group G1f having negative refractive power, and whichconsists of two negative lenses L1 and L2, 1m-th lens group G1m havingpositive refractive power and 1r-th lens group G1r having positiverefractive power, which are in this order from the object side, andfocusing is performed by moving 1m-th lens group G1m in the direction ofan optical axis. This structure can suppress a fluctuation of the heightof rays caused by focusing. Therefore, it is possible to reduce theclosest distance of focus. Further, it is possible to suppress a changein the imaging range caused by focusing.

Here, 1f-th lens group G1f consists of concave meniscus lens L1 with itsconvex surface facing the object side and negative lens L2, which are inthis order from the object side. This structure can prevent distortionon the wide-angle side from becoming worse, and suppress a high-orderspherical aberration at a telephoto end.

Further, 1m-th lens group G1m is a cemented lens consisting of concavemeniscus lens L3 with its convex surface facing the object side andbiconvex lens L4, which are in this order from the object side. Thisstructure can suppress fluctuation of various aberrations duringfocusing while the weight of a focusing lens is suppressed to be light.

Further, 1r-th lens group G1r consists of positive 1r1-th lens L5 withits strong convex surface facing the object side, biconvex 1r2-th lensL6, and convex meniscus 1r3-th lens L7 with its convex surface facingthe object side, which are in this order from the object side. Thisstructure of 1r-th lens group G1r can suppress fluctuations of aspherical aberration and astigmatism during magnification change.

Further, when the average refractive index of positive 1r1-th lens L5and biconvex 1r2-th lens L6 is N1r12, and the average Abbe number ofpositive 1r1-th lens L5 and biconvex 1r2-th lens L6 is ν1r12, and therefractive index of 1r3-th lens L7 is N1r3, and the Abbe number of1r3-th lens L7 is ν1r3, the following conditional formula (3) issatisfied. If the value is lower than the lower limit of conditionalformula (3), it becomes difficult to suppress astigmatism in aperipheral area at a wide-angle end.0.20<N1r3−N1r12  (3)

Further, when the average refractive index of positive 1r1-th lens L5and biconvex lens 1r2-th lens L6 is N1r12, and the average Abbe numberof positive 1r1-th lens L5 and biconvex 1r2-th lens L6 is ν1r12, and therefractive index of 1r3-th lens L7 is N1r3, and the Abbe number of1r3-th lens L7 is ν1r3, the following conditional formula (4) issatisfied. If the value is lower than the lower limit of conditionalformula (4), it becomes difficult to balance a lateral chromaticaberration in a middle angle of view and a lateral chromatic aberrationin a peripheral angle of view at a wide-angle end.20<ν1r12−ν1r3  (4)

Further, each of 1f-th lens group G1f and 1r-th lens group G1r includesat least an aspherical surface. When an aspherical surface is used in1f-th lens group G1f, it is possible to prevent an increase ofdistortion at a wide-angle end. When an aspherical surface is used in1r-th lens group G1r, it is possible to suppress a spherical aberrationat a telephoto end.

It is more desirable that the variable magnification optical systemaccording to an embodiment of the present invention satisfies thefollowing conditional formulas (1-1), (3-1) and (4-1) instead of theaforementioned conditional formulas (1), (3) and (4), respectively. Whenconditional formulas (1-1), (3-1) and (4-1) are satisfied, it ispossible to further enhance the effects achievable by satisfyingconditional formulas (1), (3) and (4), respectively. As a desirablemode, it is not always necessary that all of conditional formulas (1-1),(3-1) and (4-1) are satisfied at the same time. One of conditionalformulas (1-1), (3-1) and (4-1), or an arbitrary combination of themshould be satisfied.0.20<f2/f3<1.60  (1-1)0.29<N1r3−N1r12  (3-1)40<ν1r12−ν1r3  (4-1)

In the variable magnification optical system according to an embodimentof the present invention, it is desirable that glass is used as aspecific material arranged on the most object-side. Alternatively, atransparent ceramic may be used.

As the material of a lens on which an aspherical shape is formed, glassmay be used. Alternatively, plastic may be used. When plastic is used,it is possible to reduce the weight and the cost of the lens.

When the variable magnification optical system according to anembodiment of the present embodiment is used in tough conditions, it isdesirable that a multi-layer coating for protection is applied. Besidesthe coating for protection, an anti-reflection coating for reducingghost light or the like in usage may be applied.

In the example illustrated in FIG. 1, optical members PP1 and PP2 arearranged between the lens system and image plane Sim. Instead ofarranging various filters, such as a low-pass filter and a filter thatcuts a specific wavelength band, or the like, the various filters may bearranged between lenses. Alternatively, a coating having similar actionto that of various filters may be applied to a lens surface of one ofthe lenses.

Next, numerical value examples of the variable magnification opticalsystem of the present invention will be described. FIG. 1, Sections A, Band C illustrate arrangement of lenses of the variable magnificationoptical system in Example 1 at a wide-angle end, in a middle focallength state and at a telephoto end, respectively. In FIG. 1, Sections Athrough C, optical member PP is also illustrated, and the left side isthe object side, and the right side is the image side. The illustratedaperture stop St does not necessarily represent the size nor the shapeof aperture stop St, but represents the position of aperture stop St onoptical axis Z.

Similarly, FIG. 2, Sections A, B and C illustrate arrangement of lensesof the variable magnification optical system in Example 2 at awide-angle end, in a middle focal length state, and at a telephoto end,respectively. FIG. 3, Sections A, B and C illustrate arrangement oflenses of the variable magnification optical system in Example 3 at awide-angle end, in a middle focal length state, and at a telephoto end,respectively. FIG. 4, Sections A, B and C illustrate arrangement oflenses of the variable magnification optical system in Example 4 at awide-angle end, in a middle focal length state, and at a telephoto end,respectively. FIG. 5, Sections A, B and C illustrate arrangement oflenses of the variable magnification optical system in Example 5 at awide-angle end, in a middle focal length state, and at a telephoto end,respectively. FIG. 6, Sections A, B and C illustrate arrangement oflenses of the variable magnification optical system in Example 6 at awide-angle end, in a middle focal length state, and at a telephoto end,respectively.

Table 1 shows basic lens data about a variable magnification opticalsystem in Example 1, and Table 2 shows data about variablemagnification. Table 3 shows data about focus, and Table 4 and Table 5show aspherical surface data. Similarly, Table 6 through Table 30 showbasic lens data, data about variable magnification, data about focus andaspherical surface data of variable magnification optical systems inExamples 2 through 6. Next, the meanings of signs in the tables will bedescribed, using the tables of Example 1 as an example. The meaning ofthe signs in the tables of Examples 2 through 6 is basically similar toExample 1.

In the basic lens data of Table 1, the column of Si shows the surfacenumbers of i-th (i=1, 2, 3, . . . ) surfaces. The surface number of themost object-side surface of elements is the first surface, and thesurface numbers sequentially increase toward the image side. The columnof Ri shows the curvature radius of the i-th surface. The column of Dishows a distance, on optical axis Z, between the i-th surface and the(i+1)th surface. The column of Ndi shows the refractive index of amedium between the i-th surface and the (i+1)th surface for d-line(wavelength is 587.6 nm), and the column of νdj shows the Abbe number ofthe j-th (j=1, 2, 3, . . . ) optical element for d-line when the mostobject-side optical element is the first optical element, and the valueof j sequentially increases toward the image side. Further, the columnof θg, f shows partial dispersion ratio of each optical element.

The sign of a curvature radius is positive when the shape of a surfaceis convex toward the object side, and negative when the shape of asurface is convex toward the image side. The basic lens data includeaperture stop St and optical member PP. In the column of surfacenumbers, the term “(STOP)” is written for a surface corresponding toaperture stop St together with the surface number.

In the basic lens data of Table 1, “DD[SURFACE NUMBER]” is written ineach row of a surface distance that changes during magnification change.“DD [4]” is a distance between 1f-th lens group G1f and 1m-th lens groupG1m, and “DD [7]” is a distance between 1m-th lens group G1m and 1r-thlens group G1r, and “DD[13]” is a distance between first lens group G1and second lens group G2. “DD[15]” is a distance between second lensgroup G2 and third lens group G3, and “DD[23]” is a distance betweenthird lens group G3 and fourth lens group G4, and “DD[26]” is a distancebetween fourth lens group G4 and aperture stop St.

Data about variable magnification in Table 2 show a zoom magnificationratio (variable magnification ratio), focal length f, back focus Bf(distance in air), F-number Fno., full angle of view 2ω and values of DD[13], DD [15], DD [23] and DD [26] at a wide-angle end, in a middlefocal length state and at a telephoto end.

Data about focus in Table 3 show values of DD [4] and DD [7] at awide-angle end, in a middle focal length state and at a telephoto end.

In the basic lens data, the data about variable magnification and thedata about focus, degree is used as the unit of angle, and mm is used asthe unit of length. However, since an optical system can be used byproportionally enlarging or reducing the optical system, otherappropriate units may be used.

In the basic lens data of Table 1, mark * is attached to the surfacenumber of an aspherical surface. Table 1 shows, as the curvature radiusof the aspherical surface, the numerical value of a paraxial curvatureradius. The aspherical surface data in Table 4 and Table 5 show surfacenumbers Si of aspherical surfaces and aspheric coefficients about theaspherical surfaces. The aspheric coefficients are values ofcoefficients KA and Am (m=3, 4, 5 . . . 16) in an aspherical equationrepresented by the following equation (A):Zd=C·h ²/{1+(1−KA·C ² ·h ²)^(1/2) }+ΣAm·h ^(m)  (A), where

Zd: depth of aspherical surface (the length of a perpendicular from apoint on the aspherical surface at height h to a flat plane thatcontacts with the vertex of the aspherical surface and is perpendicularto the optical axis),

h: height (the length from the optical axis to the lens surface),

C: the reciprocal of paraxial curvature radius, and

KA, Am: aspheric coefficients (m=3, 4, 5 . . . 16).

TABLE 1 EXAMPLE 1 • BASIC LENS DATA Si Ri Di Ndi νdj θ g, f (SURFACE(CURVATURE (SURFACE (REFRACTIVE (ABBE (PARTIAL NUMBER) RADIUS) DISTANCE)INDEX) NUMBER) DISPERSION RATIO)  *1 671.7741 3.00 1.772499 49.600.55212  2 134.8384 11.75  3 −163.3426 1.90 1.799516 42.22 0.56727  4210.1574 DD[4]  5 139.4639 2.30 1.800000 29.84 0.60178  6 73.4230 15.031.496999 81.54 0.53748  7 −176.7451 DD[7]  8 98.0153 8.34 1.433871 95.200.53733  9 −1700.9952 0.20  10 91.1102 12.24 1.433871 95.20 0.53733  11−181.3469 0.20 *12 59.3608 7.58 1.772499 49.60 0.55212  13 144.5405DD[13]  14 30.0623 0.90 2.001003 29.13 0.59952  15 15.1723 DD[15]  16116.7085 0.80 1.882997 40.76 0.56679  17 25.2660 3.11  18 −211.5945 6.251.808095 22.76 0.63073  19 −14.3520 0.80 1.816000 46.62 0.55682  2092.0752 0.17  21 29.5030 5.51 1.658441 50.88 0.55612  22 −29.5030 0.901.882997 40.76 0.56679  23 −546.6046 DD[23]  24 −25.8345 1.00 1.74399744.78 0.56560  25 53.6380 2.46 1.922860 18.90 0.64960  26 −868.6198DD[26]  27 (STOP) ∞ 2.15  28 ∞ 3.80 1.882997 40.76 0.56679  29 −47.26240.13  30 75.9172 7.14 1.583126 59.38 0.54345  31 −27.8250 1.50 1.80400046.58 0.55730  32 −253.3002 31.47  33 417.3315 4.82 1.696797 55.530.54341  34 −43.5643 0.30  35 41.4240 6.32 1.487490 70.23 0.53007  36−41.4240 1.60 1.882997 40.76 0.56679  37 33.7835 2.40  38 34.1563 8.351.496999 81.54 0.53748  39 −22.4200 1.50 1.806100 33.27 0.58845  40−244.3828 0.12  41 75.8080 5.36 1.567322 42.82 0.57309  42 −39.8974 0.20 43 ∞ 1.00 1.516330 64.14 0.53531  44 ∞ 0.00  45 ∞ 33.00 1.608589 46.440.56664  46 ∞ 13.20 1.516329 64.10 0.53463  47 ∞ 11.68

TABLE 2 EXAMPLE 1 • DATA ABOUT VARIABLE MAGNIFICATION WIDE-ANGLE ENDMIDDLE TELEPHOTO END ZOOM 1.0 5.7 18.2 MAGNIFICATION RATIO f 7.62 43.46138.77 Bf 40.90 40.90 40.90 FNo. 1.87 1.87 2.71 2ω[°] 74.64 14.22 4.53DD[13] 0.80 37.85 46.09 DD[15] 7.68 11.68 14.68 DD[23] 49.52 5.74 5.56DD[26] 9.60 12.33 1.27

TABLE 3 EXAMPLE 1 • DATA ABOUT FOCUS inf 3m 0.55m DD[4] 1.01 3.83 14.49DD[7] 14.08 11.27 0.60

TABLE 4 EXAMPLE 1 • ASPHERICAL SURFACE DATA(1) SURFACE NUMBER 1 KA−1.144658E+02 A3    1.266635E−06 A4  −7.680904E−07 A5    1.835455E−07A6  −1.799087E−08 A7    1.017818E−09 A8  −3.276256E−11 A9   5.233524E−13 A10 −6.219345E−15 A11   4.254304E−16 A12 −1.872576E−17A13   3.233753E−19 A14 −7.119809E−22 A15 −4.166246E−23 A16  3.616030E−25

TABLE 5 EXAMPLE 1 • ASPHERICAL SURFACE DATA(2) SURFACE NUMBER 12 KA  9.454836E−01 A3  −4.681704E−07 A4  −8.801168E−08 A5  −2.733358E−08 A6   6.617664E−10 A7    5.655299E−11 A8  −4.406643E−12 A9    4.336422E−14A10   3.637359E−15 A11 −1.252064E−17 A12 −6.278635E−18 A13  1.083594E−19 A14   3.928111E−21 A15 −1.431683E−22 A16   1.282501E−24

TABLE 6 EXAMPLE 2 • BASIC LENS DATA Si Ri Di Ndi νdj θ g, f (SURFACE(CURVATURE (SURFACE (REFRACTIVE (ABBE (PARTIAL NUMBER) RADIUS) DISTANCE)INDEX) NUMBER) DISPERSION RATIO)  *1 1118.1599 3.00 1.772499 49.600.55212  2 134.0215 10.85  3 −197.8726 1.90 1.799516 42.22 0.56727  4214.3676 DD[4]  5 156.0336 2.30 1.800000 29.84 0.60178  6 77.2465 15.021.496999 81.54 0.53748  7 −155.1544 DD[7]  8 116.2018 7.57 1.43387195.20 0.53733  9 −1319.3557 0.20  10 95.9125 12.94 1.433871 95.200.53733  11 −153.7147 0.20 *12 60.8312 7.89 1.743198 49.34 0.55312  13146.9923 DD[13]  14 34.0446 0.80 2.001003 29.13 0.59952  15 15.5818DD[15]  16 120.5438 0.80 1.882997 40.76 0.56679  17 28.2452 2.67  18−472.6907 6.19 1.808095 22.76 0.63073  19 −14.6590 0.80 1.816000 46.620.55682  20 71.7680 0.15  21 30.0934 5.40 1.712995 53.87 0.54587  22−30.0934 0.90 1.882997 40.76 0.56679  23 −959.3350 DD[23]  24 −24.80471.00 1.756998 47.82 0.55662  25 53.0499 2.39 1.922860 18.90 0.64960  26−797.1480 DD[26]  27 (STOP) ∞ 2.48  28 −278.8115 3.49 1.882997 40.760.56679  29 −45.4383 0.12  30 60.0639 7.21 1.603112 60.64 0.54148  31−30.4146 1.50 1.804000 46.58 0.55730  32 −369.2199 31.88  33 719.15644.60 1.696797 55.53 0.54341  34 −45.0329 0.53  35 43.4947 6.14 1.48749070.23 0.53007  36 −45.0578 1.60 1.882997 40.76 0.56679  37 35.5739 3.15 38 35.2860 8.12 1.496999 81.54 0.53748  39 −23.1235 1.50 1.806100 33.270.58845  40 −186.2093 0.12  41 60.2392 5.22 1.540720 47.23 0.56511  42−46.9134 0.20  43 ∞ 1.00 1.516330 64.14 0.53531  44 ∞ 0.00  45 ∞ 33.001.608589 46.44 0.56664  46 ∞ 13.20 1.516329 64.10 0.53463  47 ∞ 11.02

TABLE 7 EXAMPLE 2 • DATA ABOUT VARIABLE MAGNIFICATION WIDE-ANGLE ENDMIDDLE TELEPHOTO END ZOOM 1.0 5.7 18.2 MAGNIFICATION RATIO f 7.64 43.55139.05 Bf 40.24 40.24 40.24 FNo. 1.87 1.87 2.72 2ω[°] 74.49 14.23 4.53DD[13] 0.80 40.25 49.38 DD[15] 7.21 11.21 14.21 DD[23] 49.77 4.20 3.27DD[26] 10.64 12.76 1.56

TABLE 8 EXAMPLE 2 • DATA ABOUT FOCUS inf 3m 0.55m DD[4] 1.00 3.92 14.97DD[7] 14.56 11.64 0.59

TABLE 9 EXAMPLE 2 • ASPHERICAL SURFACE DATA(1) SURFACE NUMBER 1 KA−4.58137E+02 A3    5.16186E−06 A4  −1.32039E−06 A5    2.51247E−07 A6 −2.76734E−08 A7    1.94629E−09 A8  −8.79742E−11 A9    2.49075E−12 A10−4.22860E−14 A11   4.74370E−16 A12 −8.93631E−18 A13   2.62159E−19 A14−4.54316E−21 A15   3.85676E−23 A16 −1.29271E−25

TABLE 10 EXAMPLE 2 • ASPHERICAL SURFACE DATA(2) SURFACE NUMBER 12 KA  9.61547E−01 A3  −2.62582E−06 A4    4.45866E−07 A5  −1.10434E−07 A6   1.08058E−08 A7  −6.30961E−10 A8    1.75806E−11 A9    8.12145E−14 A10−1.73754E−14 A11   1.07011E−16 A12   1.64768E−17 A13 −3.33030E−19 A14−5.84026E−21 A15   2.48068E−22 A16 −2.17774E−24

TABLE 11 EXAMPLE 3 • BASIC LENS DATA Si Ri Di Ndi νdj θ g, f (SURFACE(CURVATURE (SURFACE (REFRACTIVE (ABBE (PARTIAL NUMBER) RADIUS) DISTANCE)INDEX) NUMBER) DISPERSION RATIO)  *1 992.2898 3.00 1.772499 49.600.55212  2 127.8302 11.05  3 −202.6024 1.90 1.834807 42.73 0.56486  4205.5604 DD[4]  5 152.5617 2.30 1.800000 29.84 0.60178  6 75.6948 15.241.496999 81.54 0.53748  7 −155.1398 DD[7]  8 118.6128 6.61 1.43387195.20 0.53733  9 3239.8919 0.20  10 96.9841 13.61 1.433871 95.20 0.53733 11 −130.0249 0.20 *12 58.2585 7.66 1.772499 49.60 0.55212  13 135.2680DD[13]  14 25.4986 0.80 2.003300 28.27 0.59802  15 16.0567 DD[15]  16326.9593 0.80 1.903658 31.32 0.59481  17 21.9588 3.35  18 −477.0272 6.001.808095 22.76 0.63073  19 −15.0500 0.80 1.816000 46.62 0.55682  20114.4553 0.22  21 27.5234 5.72 1.595509 39.24 0.58043  22 −28.0326 0.901.882997 40.76 0.56679  23 −470.6662 DD[23]  24 −25.5089 1.00 1.65844150.88 0.55612  25 62.1801 2.12 1.922860 18.90 0.64960  26 1386.7600DD[26]  27 (STOP) ∞ 2.38  28 −168.7501 3.25 1.882997 40.76 0.56679  29−45.4086 0.19  30 54.0744 7.41 1.583126 59.38 0.54345  31 −29.4883 1.501.804000 46.58 0.55730  32 −273.7251 32.84  33 −420.3840 4.33 1.79951642.22 0.56727  34 −42.6096 0.30  35 41.7533 6.26 1.487490 70.23 0.53007 36 −42.5170 1.60 1.882997 40.76 0.56679  37 35.1796 0.75  38 33.28308.60 1.496999 81.54 0.53748  39 −21.4796 1.50 1.806100 33.27 0.58845  40−241.8010 0.12  41 58.8687 5.63 1.531717 48.84 0.56309  42 −41.3435 0.20 43 ∞ 1.00 1.516330 64.14 0.53531  44 ∞ 0.00  45 ∞ 33.00 1.608589 46.440.56664  46 ∞ 13.20 1.516329 64.10 0.53463  47 ∞ 12.01

TABLE 12 EXAMPLE 3 • DATA ABOUT VARIABLE MAGNIFICATION WIDE-ANGLE ENDMIDDLE TELEPHOTO END ZOOM 1.0 5.7 18.2 MAGNIFICATION RATIO f 7.63 43.51138.92 Bf 41.23 41.23 41.23 FNo. 1.87 1.87 2.74 2ω[°] 74.64 14.21 4.52DD[13] 0.80 38.40 46.83 DD[15] 8.25 12.25 15.25 DD[23] 49.28 3.48 4.15DD[26] 9.19 13.38 1.30

TABLE 13 EXAMPLE 3 • DATA ABOUT FOCUS inf 3m 0.55m DD[4] 1.01 3.73 14.08DD[7] 13.67 10.95 0.59

TABLE 14 EXAMPLE 3 • ASPHERICAL SURFACE DATA(1) SURFACE NUMBER 1 KA−4.468497E+01 A3    2.777523E−06 A4  −1.060854E−06 A5    1.873957E−07A6  −1.617402E−08 A7    8.274842E−10 A8  −2.532251E−11 A9   4.543772E−13 A10 −7.531673E−15 A11   2.430208E−16 A12 −3.513915E−18A13 −1.593706E−19 A14   7.513811E−21 A15 −1.179792E−22 A16  6.701519E−25

TABLE 15 EXAMPLE 3 • ASPHERICAL SURFACE DATA(2) SURFACE NUMBER 12 KA  9.762715E−01 A3  −1.967016E−06 A4    6.067136E−07 A5  −1.852765E−07A6    2.475162E−08 A7  −2.265087E−09 A8    1.402363E−10 A9 −5.831184E−12 A10   1.628599E−13 A11 −3.370140E−15 A12   7.337566E−17A13 −1.908439E−18 A14   3.789332E−20 A15 −4.123364E−22 A16  1.779160E−24

TABLE 16 EXAMPLE 4 • BASIC LENS DATA θ g, f Si Ri Di Ndi ν dj (PARTIAL(SURFACE (CURVATURE (SURFACE (REFRACTIVE (ABBE DISPERSION NUMBER)RADIUS) DISTANCE) INDEX) NUMBER) RATIO)  *1 −1080.8974 2.80 1.80400046.58 0.55730   2 135.8985 9.79   3 −257.7360 1.90 1.834807 42.730.56486   4 440.7035 DD[4]    5 156.1196 2.10 1.800000 29.84 0.60178   681.1824 14.33  1.496999 81.54 0.53748   7 −174.0494 DD[7]    8 117.14167.06 1.433871 95.20 0.53733   9 3789.5474 0.20  10 128.8708 10.95 1.433871 95.20 0.53733  11 −153.5083 0.20 *12 55.6993 8.50 1.72915754.68 0.54451  13 140.8106 DD[13]  14 46.2979 0.80 2.001003 29.130.59952  15 16.2016 DD[15]  16 91.1180 0.80 1.903658 31.32 0.59481  1734.4758 2.43  18 −656.5355 6.50 1.805181 25.42 0.61616  19 −14.2544 0.801.746931 50.95 0.54910  20 43.7667 1.01  21 29.0914 5.63 1.658441 50.880.55612  22 −28.7417 0.80 1.882997 40.76 0.56679  23 −200.0704 DD[23] 24 −25.9687 0.80 1.772499 49.60 0.55212  25 55.2918 2.39 1.922860 18.900.64960  26 −768.2726 DD[26]  27 (STOP) ∞ 2.30  28 −208.8837 3.531.882997 40.76 0.56679  29 −43.0643 0.55  30 79.9057 7.16 1.650996 56.160.54818  31 −27.9833 1.20 1.804000 46.58 0.55730  32 −386.4888 33.00  33 −330.4341 4.29 1.696797 55.53 0.54341  34 −41.1004 0.76  35 48.52235.96 1.487490 70.23 0.53007  36 −41.9805 1.60 1.882997 40.76 0.56679  3745.0118 1.59  38 41.6540 7.70 1.496999 81.54 0.53748  39 −23.4390 1.201.806100 33.27 0.58845  40 −139.2414 0.61  41 64.0318 5.25 1.51741752.43 0.55649  42 −45.5434 0.20  43 ∞ 1.00 1.516330 64.14 0.53531  44 ∞0.00  45 ∞ 33.00  1.608589 46.44 0.56664  46 ∞ 13.20  1.516329 64.100.53463  47 ∞ 11.94 

TABLE 17 EXAMPLE 4 • DATA ABOUT VARIABLE MAGNIFICATION WIDE-ANGLETELEPHOTO END MIDDLE END ZOOM 1.0 5.7 18.3 MAGNIFICATION RATIO f 7.6443.72 139.88 Bf 41.16 41.16 41.16 FNo. 1.87 1.87 2.71 2ω [°] 74.39 14.214.50 DD[13] 0.80 41.64 50.88 DD[15] 6.77 11.27 14.77 DD[23] 50.61 4.083.44 DD[26] 12.16 13.35 1.25

TABLE 18 EXAMPLE 4 • DATA ABOUT FOCUS inf 3m 0.55m DD[4] 1.00 4.37 17.02DD[7] 16.61 13.25 0.59

TABLE 19 EXAMPLE 4 • ASPHERICAL SURFACE DATA(1) SURFACE NUMBER 1 KA−1.638686E+03 A3 −7.984087E−07 A4 −7.445182E−07 A5  1.455516E−07 A6−1.209683E−08 A7  4.480628E−10 A8  9.212129E−13 A9 −6.783062E−13 A10 1.950646E−14 A11  1.511816E−17 A12 −7.066382E−18 A13 −8.845084E−20 A14 7.960287E−21 A15 −1.346019E−22 A16  7.617207E−25

TABLE 20 EXAMPLE 4 • ASPHERICAL SURFACE DATA(2) SURFACE NUMBER 12 KA9.599348E−01 A3 4.508169E−07 A4 −4.588327E−08  A5 −1.814323E−08  A6−2.546687E−10  A7 9.137975E−11 A8 −3.140506E−12  A9 −6.383125E−14  A103.345302E−15 A11 1.490242E−16 A12 −9.156579E−18  A13 8.923339E−20 A142.994286E−21 A15 −7.461677E−23  A16 4.697905E−25

TABLE 21 EXAMPLE 5 • BASIC LENS DATA θ g, f Si Ri Di Ndi ν dj (PARTIAL(SURFACE (CURVATURE (SURFACE (REFRACTIVE (ABBE DISPERSION NUMBER)RADIUS) DISTANCE) INDEX) NUMBER) RATIO)  *1 1148.5775 2.00 1.78800147.37 0.55598   2 140.6095 10.83    3 −195.6697 1.80 1.834807 42.730.56486   4 212.7958 DD[4]    5 126.7529 2.00 1.805181 25.42 0.61616   675.4660 16.38  1.438750 94.93 0.53433   7 −154.3092 DD[7]    8 101.28458.04 1.433871 95.20 0.53733   9 −16671.7552 0.20  10 86.0211 12.95 1.433871 95.20 0.53733  11 −192.9017 0.20 *12 60.0092 6.78 1.78800147.37 0.55598  13 151.5548 DD[13]  14 30.6562 0.80 2.001003 29.130.59952  15 16.6089 DD[15]  16 186.9512 0.80 1.882997 40.76 0.56679  1722.6712 3.10  18 946.0474 6.61 1.808095 22.76 0.63073  19 −14.2966 0.801.816000 46.62 0.55682  20 93.0335 0.36  21 27.5953 5.88 1.648498 53.020.55487  22 −26.2350 0.80 1.882997 40.76 0.56679  23 709.7970 DD[23]  24−24.0962 0.80 1.699998 48.08 0.55960  25 59.6189 2.26 1.922860 18.900.64960  26 −1095.0797 DD[26]  27 (STOP) ∞ 2.14  28 −309.2427 3.651.882997 40.76 0.56679  29 −42.6250 0.12  30 62.1599 6.85 1.563839 60.670.54030  31 −31.2361 1.20 1.804000 46.58 0.55730  32 −350.1700 35.55  33 1728.0143 4.55 1.696797 55.53 0.54341  34 −43.4526 0.30  35 42.02106.15 1.487490 70.23 0.53007  36 −43.4961 1.60 1.882997 40.76 0.56679  3736.7305 0.12  38 33.4089 8.16 1.496999 81.54 0.53748  39 −23.5594 1.501.806100 33.27 0.58845  40 −329.1716 0.12  41 64.6880 5.12 1.56732242.82 0.57309  42 −46.3994 0.20  43 ∞ 1.00 1.516330 64.14 0.53531  44 ∞0.00  45 ∞ 33.00  1.608589 46.44 0.56664  46 ∞ 13.20  1.516329 64.100.53463  47 ∞ 11.60 

TABLE 22 EXAMPLE 5 • DATA ABOUT VARIABLE MAGNIFICATION WIDE-ANGLETELEPHOTO END MIDDLE END ZOOM 1.0 5.7 18.2 MAGNIFICATION RATIO f 7.6143.37 138.48 Bf 40.82 40.82 40.82 FNo. 1.87 1.87 2.73 2ω [°] 74.60 14.244.54 DD[13] 0.80 37.00 45.04 DD[15] 7.64 11.64 14.64 DD[23] 47.67 4.504.84 DD[26] 9.67 12.64 1.26

TABLE 23 EXAMPLE 5 • DATA ABOUT FOCUS inf 3m 0.55m DD[4] 1.00 3.89 14.83DD[7] 14.42 11.53 0.59

TABLE 24 EXAMPLE 5 • ASPHERICAL SURFACE DATA(1) SURFACE NUMBER 1 KA−1.292987E+02  A3 2.440017E−06 A4 −8.390146E−07  A5 1.546545E−07 A6−1.164077E−08  A7 4.013569E−10 A8 1.146383E−12 A9 −6.186674E−13  A101.884950E−14 A11 7.155295E−18 A12 −1.177701E−17  A13 2.107606E−19 A146.021065E−22 A15 −5.102732E−23  A16 3.970978E−25

TABLE 25 EXAMPLE 5 • ASPHERICAL SURFACE DATA(2) SURFACE NUMBER 12 KA9.145537E−01 A3 −1.201768E−06  A4 9.649789E−08 A5 −6.336666E−08  A66.014201E−09 A7 −4.254424E−10  A8 1.961689E−11 A9 −4.640334E−13  A106.193828E−16 A11 4.537461E−17 A12 1.224673E−17 A13 −5.359197E−19  A146.392771E−21 A15 3.632484E−23 A16 −9.107176E−25 

TABLE 26 EXAMPLE 6 • BASIC LENS DATA θ g, f Si Ri Di Ndi ν dj (PARTIAL(SURFACE (CURVATURE (SURFACE (REFRACTIVE (ABBE DISPERSION NUMBER)RADIUS) DISTANCE) INDEX) NUMBER) RATIO)  *1 3050.5864 3.00 1.77249949.60 0.55212   2 155.4752 10.53    3 −183.0713 1.90 1.806098 40.920.57019   4 214.7203 DD[4]    5 135.6184 2.30 1.800000 29.84 0.60178   673.1906 14.48  1.496999 81.54 0.53748   7 −204.5823 DD[7]    8 93.22679.30 1.433871 95.20 0.53733   9 −1004.4591 0.15  10 86.7192 12.02 1.433871 95.20 0.53733  11 −225.9939 0.15 *12 61.5434 7.63 1.77249949.60 0.55212  13 160.2760 DD[13]  14 32.0360 0.80 2.001003 29.130.59952  15 15.6085 DD[15]  16 122.1226 0.80 1.882997 40.76 0.56679  1724.5558 3.08  18 −263.9081 5.83 1.808095 22.76 0.63073  19 −14.7147 0.801.816000 46.62 0.55682  20 62.2098 0.12  21 29.0602 5.82 1.658441 50.880.55612  22 −27.6414 0.90 1.882997 40.76 0.56679  23 −109.3731 DD[23] 24 −23.7371 1.00 1.743997 44.78 0.56560  25 54.1151 2.18 1.922860 18.900.64960  26 −469.8193 DD[26]  27 (STOP) ∞ 1.99  28 −363.1046 3.581.882997 40.76 0.56679  29 −43.9952 0.20  30 93.7337 7.07 1.589130 61.140.54067  31 −25.6186 1.50 1.772499 49.60 0.55212  32 −146.0468 31.89  33 390.3807 5.21 1.696797 55.53 0.54341  34 −40.8550 0.71  35 61.89176.39 1.487490 70.23 0.53007  36 −32.4830 1.60 1.882997 40.76 0.56679  3759.4043 2.67  38 72.0074 7.28 1.496999 81.54 0.53748  39 −20.2283 1.501.800000 29.84 0.60178  40 −134.4753 1.03  41 81.8770 5.74 1.58143940.75 0.57757  42 −37.2180 0.20  43 ∞ 1.00 1.516330 64.14 0.53531  44 ∞0.00  45 ∞ 33.00  1.608589 46.44 0.56664  46 ∞ 13.20  1.516329 64.100.53463  47 ∞ 10.51 

TABLE 27 EXAMPLE 6 • DATA ABOUT VARIABLE MAGNIFICATION WIDE-ANGLETELEPHOTO END MIDDLE END ZOOM 1.0 5.7 18.3 MAGNIFICATION RATIO f 7.6343.62 139.55 Bf 39.73 39.73 39.73 FNo. 1.87 1.87 2.71 2ω [°] 74.72 14.174.50 DD[13] 0.80 37.29 45.23 DD[15] 7.57 11.87 14.57 DD[23] 47.17 4.865.92 DD[26] 11.27 12.79 1.09

TABLE 28 EXAMPLE 6 • DATA ABOUT FOCUS inf 3m 0.55m DD[4] 1.03 4.12 15.76DD[7] 15.32 12.23 0.59

TABLE 29 EXAMPLE 6 • ASPHERICAL SURFACE DATA(1) SURFACE NUMBER 1 KA−5.262102E+01  A3 1.478393E−06 A4 6.136511E−07 A5 −2.043531E−07  A63.143525E−08 A7 −2.527448E−09  A8 1.110050E−10 A9 −2.303459E−12  A106.442931E−15 A11 −4.126190E−16  A12 8.422049E−17 A13 −3.588192E−18  A147.234282E−20 A15 −7.388562E−22  A16 3.096807E−24

TABLE 30 EXAMPLE 6 • ASPHERICAL SURFACE DATA(2) SURFACE NUMBER 12 KA9.083037E−01 A3 −2.063300E−06  A4 3.148055E−08 A5 −3.469585E−08  A68.909404E−10 A7 4.382904E−11 A8 −3.852300E−12  A9 5.095699E−14 A104.710080E−15 A11 −2.760229E−16  A12 6.190504E−18 A13 8.407242E−21 A14−4.145739E−21  A15 9.610231E−23 A16 −7.468715E−25 

Table 31 shows values corresponding to conditional formulas (1) through(4) for the variable magnification optical systems in Examples 1 through6. In all of the examples, d-line is a reference wavelength. Values inthe tables of data at the aforementioned variable magnification and thefollowing Table 31 show values at the reference wavelength.

TABLE 31 FORMULA CONDITIONAL NUMBER FORMULA EXAMPLE 1 EXAMPLE 2 EXAMPLE3 EXAMPLE 4 EXAMPLE 5 EXAMPLE 6 (1) 0.10 > f2/f3 < 2.00 0.734 0.5141.515 0.252 1.066 0.652 (2) 2.0 ≦ LN2 2.00100 2.00100 2.00330 2.001002.00100 2.00100 (3) 0.20 < N1r3 − N1r12 0.33863 0.30933 0.33863 0.295290.35413 0.33863 (4) 20 < ν 1r12 − ν 1r3 45.60 45.86 45.60 40.52 47.8345.60

FIG. 7, Sections A through L show aberration diagrams of the variablemagnification optical system in Example 1. FIG. 7, Sections A, B, C andD illustrate a spherical aberration, astigmatism, distortion aberration(distortion) and a lateral chromatic aberration at a wide-angle end,respectively. FIG. 7, Sections E, F, G and H illustrate a sphericalaberration, astigmatism, distortion aberration (distortion) and alateral chromatic aberration in a middle focal length state,respectively. FIG. 7, Sections I, J, K and L illustrate a sphericalaberration, astigmatism, distortion aberration (distortion) and alateral chromatic aberration at a telephoto end, respectively.

Each aberration diagram illustrating the spherical aberration,astigmatism and distortion (distortion aberration) shows an aberrationwhen d-line (wavelength is 587.6 nm) is a reference wavelength. In thediagram of the spherical aberration and the diagram of the lateralchromatic aberration, a solid line, a long broken line, a short brokenline and a gray line indicate aberrations for d-line (wavelength is587.6 nm), C-line (wavelength is 656.3 nm), F-line (wavelength is 486.1nm) and g-line (wavelength is 435.8 nm), respectively. In the diagram ofthe astigmatism, an aberration in a sagittal direction and an aberrationin a tangential direction are indicated by a solid line and a brokenline, respectively. In the diagram of the spherical aberration, Fno.represents an F-number. In the other diagrams, ω represents a half angleof view.

Similarly, FIG. 8, Sections A through L show aberration diagrams of thevariable magnification optical system in Example 2 at a wide-angle end,in a middle focal length state, and at a telephoto end. FIG. 9, SectionsA through L show aberration diagrams of the variable magnificationoptical system in Example 3 at a wide-angle end, in a middle focallength state, and at a telephoto end. FIG. 10, Sections A through L showaberration diagrams of the variable magnification optical system inExample 4 at a wide-angle end, in a middle focal length state, and at atelephoto end. FIG. 11, Sections A through L show aberration diagrams ofthe variable magnification optical system in Example 5 at a wide-angleend, in a middle focal length state, and at a telephoto end. FIG. 12,Sections A through L show aberration diagrams of the variablemagnification optical system in Example 6 at a wide-angle end, in amiddle focal length state, and at a telephoto end.

As these kinds of data show, all of the variable magnification opticalsystems in Examples 1 through 6 satisfy conditional formulas (1) through(4). It is recognized that they have excellent optical performance whilethe size of the optical system is small and the weight is light.

Next, an imaging apparatus according to an embodiment of the presentinvention will be described. FIG. 13 is a schematic diagram illustratingthe configuration of an imaging apparatus using the variablemagnification optical system according to an embodiment of the presentinvention, as an example of an imaging apparatus according to anembodiment of the present invention. The imaging apparatus is, forexample, a surveillance camera, a video camera, an electronic stillcamera or the like using a solid-state imaging device, such as a CCD anda CMOS, as a recording medium.

An imaging apparatus 10 illustrated in FIG. 13 includes the variablemagnification optical system 1, a filter 2 arranged on the image side ofthe variable magnification optical system 1, an imaging device 3 thatimages an image of a subject formed by the variable magnificationoptical system, a signal processing unit 4 that performs operationprocessing on a signal output from the imaging device 3, and a zoomcontrol unit 5 for performing magnification change of the variablemagnification optical system 1 and focus adjustment necessitated by themagnification change.

The variable magnification optical system 1 includes first lens group G1having positive refractive power, and which is fixed duringmagnification change, second lens group G2 having negative refractivepower, and which moves during magnification change, third lens group G3having negative refractive power, and which moves during magnificationchange, fourth lens group G4 having negative refractive power, and whichmoves during magnification change, aperture stop St, which is fixedduring magnification change, and fifth lens group G5 having positiverefractive power, and which is fixed during magnification change, whichare in this order from an object side.

In FIG. 13, each lens group is schematically illustrated. The imagingdevice 3 converts an optical image formed by the variable magnificationoptical system 1 into electrical signals. The imaging device 3 isarranged in such a manner that the imaging surface of the imaging device3 is located at the same position as the image plane of the variablemagnification optical system. For example, a CCD, a CMOS or the like maybe used as the imaging device 3.

So far, the present invention has been described by using embodimentsand examples. However, the present invention is not limited to theembodiments nor the examples, and various modifications are possible.For example, values, such as the curvature radius of each lens element,distances between surfaces, refractive indices, Abbe numbers andaspheric coefficients, are not limited to the values in the numericalvalue examples, but may be other values.

What is claimed is:
 1. A variable magnification optical systemconsisting of: a first lens group having positive refractive power, andwhich is fixed during magnification change; a second lens group havingnegative refractive power; a third lens group having negative refractivepower; a fourth lens group having negative refractive power; and a fifthlens group having positive refractive power, and which is fixed duringmagnification change, which are in this order from an object side,wherein the second lens group, the third lens group and the fourth lensgroup move in such a manner that a distance between the first lens groupand the second lens group constantly becomes longer and a distancebetween the second lens group and the third lens group constantlybecomes longer, compared with a wide-angle end, and a distance betweenthe third lens group and the fourth lens group changes and a distancebetween the fourth lens group and the fifth lens group changes whenmagnification is changed from the wide-angle end to a telephoto end. 2.The variable magnification optical system, as defined in claim 1,wherein the fourth lens group temporarily moves toward the object sideand reversely moves toward an image side when magnification is changedfrom the wide-angle end to the telephoto end.
 3. The variablemagnification optical system, as defined in claim 1, wherein thedistance between the third lens group and the fourth lens group is theshortest when a focal length is closer to the wide-angle end than to thetelephoto end during magnification change, and the distance at thewide-angle end is longer than the distance at the telephoto end.
 4. Thevariable magnification optical system, as defined in claim 1, whereinthe first lens group consists of a 1f-th lens group having negativerefractive power, and which consists of two negative lenses, a 1m-thlens group having positive refractive power and a 1r-th lens grouphaving positive refractive power, which are in this order from theobject side, and wherein focusing is performed by moving the 1m-th lensgroup in the direction of an optical axis.
 5. The variable magnificationoptical system, as defined in claim 4, wherein the 1m-th lens group is acemented lens consisting of a concave meniscus lens with its convexsurface facing the object side and a biconvex lens, which are in thisorder from the object side.
 6. The variable magnification opticalsystem, as defined in claim 1, wherein the following conditional formula(1) is satisfied when the focal length of the second lens group is f2and the focal length of the third lens group is f3:0.10<f2/f3<2.00  (1).
 7. The variable magnification optical system, asdefined in claim 6, wherein the following conditional formula (1-1) issatisfied:0.20<f2/f3<1.60  (1-1).
 8. The variable magnification optical system, asdefined in claim 1, wherein the second lens group consists of only aconcave meniscus lens with its convex surface facing the object side. 9.The variable magnification optical system, as defined in claim 8,wherein the following conditional formula (2) is satisfied when therefractive index of the concave meniscus lens is LN2:2.0≦LN2  (2).
 10. An imaging apparatus comprising: the variablemagnification optical system, as defined in claim 1.